如何更改SLF4J SimpleLogger文件名？

Question

My Java application uses SLF4J which I have configured to use the SimpleLogger implementation and redirect log messages to a file. That is working fine.

How do I subsequently change the name of the log file?

I have tried changing the LOG_FILE_KEY property but it seems to have no effect. The log messages continue to be output to the original log file.

This is what I've done:

System.setProperty(org.slf4j.impl.SimpleLogger.LOG_FILE_KEY, Paths.get("new-filename.txt").toString());

Answer 1

I think I figured out the answer with the help of this answer and looking at the source code for org.slf4j.impl.SimpleLogger .

The answer is you can't create a new log file as the logger properties are loaded only once - upon construction of the first logger instance. Subsequent loggers will use the same properties as the first one.

Answer 2

To set the file path to your liking, one simply has to set the following property, either in a file named simplelogger.properties on the classpath (eg by placing such a file under the resources directory) or through a -D JVM startup option.

The property name and syntax is simply:

org.slf4j.simpleLogger.logFile=your-file-path

See in this related answer for examples of providing a property through either of the two mentioned methods.